The invention relates to a method of controlling an internal combustion engine with a cylinder having at least two inlet valves, the timing of at least one of which is adjustable.
Internal combustion engines are designed to be operated over a wide rotational speed range. In order to obtain a high torque accompanied at the same time by an acceptable degree of efficiency and low exhaust gas emission values over the wide rotational speed range it is necessary to make compromises in the design of the valve geometry and the valve control system, the gas inlet system and the fuel supply. Internal combustion engines are usually operated more often in the lower rotational speed range than in the higher rotational speed range. For this reason it is particularly appropriate for a low emission of pollutants to configure an internal combustion engine in such a way that it permits efficient combustion in particular in a low rotational speed range. Diesel engines which are usually equipped with a non-adjustable valve drive because of the internal geometry of their cylinders, are a problem in terms of the emission of pollutants. The valve lifting curve is usually configured to a considerable degree according to criteria of achievable power and torque. In order to comply with exhaust gas legislation, the injection is varied and attempts are made to convert the pollutants using exhaust gas treatment techniques.
It is known that a good degree of turbulence of the combustion air flowing into the interior of the cylinders, referred to as swirl, improves the mixing of the injected fuel with the combustion air and thus results in good combustion with a high power yield and relatively low emission of pollutants. In order to generate a swirl, DE 196 06 054C2 proposes that two inlet valves per cylinder be operated in one or two opening modes with different stroke action curves. The different valve movements of the two inlet valves generate selective turbulence in the form of swirls, allowing the combustion process to be influenced and improved. DE 43 419 45 A1 also mentions, but with respect to a spark ignition engine, that the inflow conditions can be improved by selective control of the valve stroke.
It is the object of the invention to provide a method by which both, a particularly efficient combustion and a high torque can be achieved in the operation of an internal combustion engine.